This invention relates generally to a precompression pump sprayer of the type wherein a plunger rod having a discharge passage and an enlarged discharge valve seat at its lower end extends through a reciprocable piston located in the pump cylinder for sliding movement between an inactive position and an end-of-stroke position. The piston engages the valve seat in a discharge closed position and moves out of engagement with the valve seat in a discharge open position. A primary spring biases the plunger rod toward its inactive position, and a secondary spring extends between the piston and a projection on the plunger rod for transmitting movement of the plunger rod to the piston, the secondary spring having a predetermined spring force for biasing the piston toward the discharge closed position. During pump actuation, the discharge passage opens when the pump chamber pressure exceeds the force of the secondary spring.
More particularly, the present invention relates to an improvement over prior art structures of this general type by the provision of a quick acting discharge valve which avoids frictional engagement between the valve seat on the plunger rod and the piston which acts as a valve, to thereby effect more precise precompression values which avoids the dispensing of fluids at low pressures thereby avoiding dribbles, drips and drooling of product out of the discharge orifice.
Precompression pump sprayers of the general type characterized above enjoy widespread use for the fine mist spraying of liquids such as perfumes and colognes as well as may other personal care products. One of the features of the pump is to have a relatively short overall dimension, comparable in size to that of a perfume package having no pump sprayer, i.e., it is desirable for the pump sprayer to have the same cover, overcap, etc. and at the same time have its pump mechanism not visible through the glass or plastic bottle at its neck, similar to that of a package without a pump. To achieve this objective, and because the inner diameter of the typical bottle neck for such a package is of limited size, it is important to achieve maximum optimization of the height dimension of each element of the pump sprayer.
One of the many drawbacks associated with the use of non-precompression pump sprayers is its inability to quickly shut off the discharge at the end of the pressure stroke, thereby causing residual product to be discharged in dribbles and drips.
U.S. Pat. No. 4,051,983 is a precompression pump sprayer having a single piston return spring, and a conical discharge valve seated within the piston with the result that a highly acceptable fine mist spray is discharged without producing dribbles and drips or drooling on discharge shutoff.
However, the degree of precompression cannot be separately adjusted, and the precompression force varies during piston travel so that the finger force required for actuation is high. Moreover, the output of the pump in relation to the length of the stroke is low, and the pump dimensions are large in relation to the output.
U.S. Pat. No. 4,856,677 discloses a precompression pump sprayer with two springs. The overall height of the pump is low, and the full stroke is converted in output. Reduced finger force is required for pump actuation, and the two springs act in opposed relation rendering the precompression force reasonably constant during piston travel.
However, an annular seal at the lower end of the piston requires a relative sliding of the plunger rod to cover and uncover a lateral discharge port for controlling the discharge. Such an arrangement gives rise to the production of dribbles and drips and even drooling at the beginning of each pressure stroke.
U.S. Pat. No. 4,941,595, commonly owned herewith, discloses a precompression pump sprayer having a secondary cylinder affixed to the pump piston for housing a secondary piston/discharge valve mounted for sliding movement, and a secondary spring urging the secondary piston toward a discharge valve closing position.
This pump sprayer requires a low force to actuate due to the constant precompression during the stroke. A highly satisfactory fine mist spray is effected without producing dribbles and drips or drooling as abrupt and clean discharge shut off is effected by the provision of the conical discharge valve.
A wide range of products can be effectively sprayed by this known sprayer adapting the characteristics of the liquid to be sprayed by changing the secondary spring. Viscous products and gels can therefore be effectively sprayed.
However, a relatively large pump cylinder is required to accommodate the secondary cylinder.
U.S. Pat. No. 5,234,135 is similarly structured to that of the U.S. Pat. No. 4,856,677 in that frictional relative sliding movement is required between the plunger rod and the piston for covering and uncovering lateral discharge ports to control the discharge. Two springs are utilized independently, and a suck-back feature is added.
The pump requires a low force to actuate and has relatively short overall dimensions. The suck-back system at the end of the plunger stroke introduces a vacuum in a second inner chamber for avoiding the formation of dribbles and drips at the discharge orifice.
However, the frictional sliding movement necessitated between the plunger rod and the piston for controlling the discharge impedes a rapid and complete shutoff of the discharge giving rise to the production of dribbles, drips, drooling or even a reduced quality in spray. Although such prior art sprayer could be adapted to different products, in practice the range is reduced because of the low quality spray (i.e., jet) production.